1. Field of the Invention
The present invention relates to a filter protection device for use in a clean room. More particularly, the present invention relates to a filter protection device for protecting an air filter in a clean room for fabricating a semiconductor device from external disturbances, such as an unexpected impact thereon.
2. Description of the Related Art
Recently, as semiconductor devices become more highly integrated, higher purity specifications of a clean room, wherein the semiconductor devices are fabricated, have become common. A clean room is a defined space in which various facilities are installed for manufacturing the semiconductor devices, each of the facilities carrying out a respective unit process for manufacturing the semiconductor devices. Accordingly, various types of filters have been installed in air ducts through which a plurality of pollutants, such as harmful gases or particles of dust, are provided to prevent a process failure of the wafer due to contamination. The various filters are classified into categories according to the filtering pollutant. A high efficiency particulate air (HEPA) filter or an ultra low penetrating air (ULPA) filter has been primarily used for capturing a first pollutant of a pulverized material, such as a minute dust in the clean room. In addition, recent clean rooms have been increasingly using a chemical filter to capture a second pollutant of harmful gases.
In order to increase a purity level of the clean room, strict maintenance of an installed filter is needed in addition to high performance of the filter. As the filter filters out the pollutants, the pollutants are settled and stacked up on the filter. Thus, the installed filter needs to be periodically replaced. Therefore, the installed filter is periodically inspected for damage and is then repaired or replaced depending on the results of the inspection, thereby preventing a process failure caused by contamination due to poor filter performance.
However, recent needs for semiconductor devices have diversified and the life cycle of a semiconductor device now has a tendency to be short. Therefore, a layout of the facilities in a clean room is frequently changed to rapidly respond to a market demand for a particular semiconductor device, and the filter is frequently damaged during this layout change. As a result, a processing failure of the wafer is repeatedly generated until the damaged filter is repaired or replaced as a result of a regular inspection of the filter.
FIG. 1 illustrates a plan view of a schematic structure of a conventional clean room.
Referring to FIG. 1, a conventional clean room 90 for manufacturing a semiconductor device has various cells 10 for performing the unit process. The various cells 10 are systematically connected to each other in the clean room. In the clean room, operators move into each of the cells 10 using pathways 30. The cells 10 are systematically coupled to each other for sequentially and repeatedly performing the respective unit processes for manufacturing the semiconductor device. These unit processes may include a deposition process, a photolithographic process, an etching process, an ion implanting process, and a polishing and rinsing process. An outer wall 40 separates the clean room 90 from external surroundings. Each of the cells 10 is divided into a service area (S/A) 101 including a processing part and a wafer transporting part separated by a partition and a process station (P/S) 102. A unit process for manufacturing a semiconductor device is performed in the S/A 101, and the processed wafer is transported between the S/A 101 of different cells through the P/S 102. The operators also work in the P/S 102. Accordingly, a silicon substrate repeatedly passes through unit cells 10 of the clean room 90 during fabrication of a semiconductor device.
The clean room 90 has an internal pressure with a constant difference from the external surroundings. In addition, internal pressure differences are also formed inside the clean room 90 for reducing a failure rate caused by harmful gases and particles. The internal pressure difference in the clean room 90 may be formed by controlling an amount of air supplied to each region of the clean room 90.
FIG. 2 illustrates a cross-sectional view of an exemplary unit cell including a facility for performing a unit process, i.e., one of the sequential processes for manufacturing semiconductor devices.
Referring to FIG. 2, air is supplied through an air guiding part 52 installed at a top portion of the clean room 90, and provided into the P/S 102 and the S/A 101 after the pollutants in the air are filtered through the air filter 60. The air filter 60 may be a HEPA filter or a ULPA filter. Since the processed wafer is transferred in the P/S 102, a class, which is a unit of purity level of a clean room and is defined as a number of particles having a diameter greater than 0.3 μm in 1 cubic meter (1 m3) of air, of the P/S 102 needs to be higher than a class of the S/A 101. Generally, the P/S 102 is formed to be class 1, and the S/A 101 is formed to be class 1000. The wafer is transported into the wafer transporting part 72 through the P/S 102, and is subsequently transported into the processing part 74. The wafer undergoes a particular unit process in the processing part 74. A special air reservoir 76 is installed for supplying clean air only to the wafer transporting part 72 and the processing part 74. The air supplied through the air guiding part 52 is exhausted through a plurality of exiting tubes 54 installed at a bottom portion of the clean room 90, thereby completing an air circulation cycle.
FIG. 3 illustrates an exemplary installation of a conventional air filter.
Referring to FIG. 3, a conventional air filter 60 is positioned between the air guiding part and the S/A or the P/S, and filters the air supplied into the S/A or the P/S. The air filter 60 is inserted into a filter fixing part 62 installed on a ceiling of the S/A or the P/S to secure the air filter 60 on the ceiling of the S/A or the P/S. As a result, when the filter is determined to be damaged, the filter may be easily repaired and/or replaced with a new filter. The filter fixing part 62 is installed along a longitudinal and a latitudinal direction of the filter 60.
Each cell in the above-described clean room is arranged for performing a unit process for fabricating a particular semiconductor device, and when the type of semiconductor device to be fabricated is changed, cell arrangement in the clean room needs similarly requires change. Recent diversified demand for semiconductor devices and shortened life cycle of the semiconductor device necessitate more frequent rearrangement of the cells in the clean room, so that processing facilities and the partitions are reinstalled in the clean room 90. Therefore, the more frequent rearrangement of the cells results in more frequent occurrence of damage to a filter. In addition, a process failure rate is rapidly increased in a cell including a damaged filter, and an additional cost is added for repairing and replacing the damaged filter. Conventional maintenance work in a clean room, such as installing or removing gas pipes, installing or repairing auto-transportation equipments, or replacing with a new fluorescent lamp in the P/S, also causes the above-described filter damage thereby increasing the process failure rate and the maintenance cost.
FIGS. 4A to 4F are photographs showing examples of filter damage. FIGS. 4A and 4B show a filter partially damaged when processing facilities are installed or moved in a clean room. The damaged filter shown in FIGS. 4A and 4B needs to be repaired or replaced with a new filter according to a degree of damage to the filter. FIGS. 4C and 4D show a filter significantly damaged when a long member such as a partition is moved in the clean room. The damaged filter shown in FIGS. 4C to 4D needs to be replaced with a new filter due to the extent of the damage to the filer. FIGS. 4E and 4F show a severely filter damaged by a working instrument such as a support for the partition or a wrench. The damaged filter shown in FIGS. 4E and 4F requires replacement due to the severity of the damage.
As described above, a damaged filter in a clean room repeatedly causes a process failure, thereby increasing a maintenance cost for the air filter. Filter maintenance costs have increased as the layout of the clean room needs to be more frequently changed in response to recent demand for particular semiconductor devices.